Gm allotype associated resistance and susceptibility to alopecia areata.

IgG heavy chain (Gm) and kappa light chain (Km) allotypes were determined in 42 Caucasian patients with alopecia areata. There was a significant increase in frequency of Gm 1,2,3,17;5,13,21 (P less than 0.001), and a significant decrease in frequency of Gm 1,3,17;5,13,21 (P = 0.009), when results were compared to those of 105 normal healthy Caucasians from the same geographic area. These results can be explained by postulating dominant disease susceptibility and resistance genes in significant linkage disequilibrium with the haplotypes Gm1,2,17;21 and Gm1,17;21, respectively.